A stent is a medical device introduced to a body lumen and is well known in the art. Typically, a stent is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the stent in a radially reduced configuration, optionally restrained in a radially compressed configuration by a sheath and/or catheter, is delivered by a stent delivery system or “introducer” to the site where it is required. The introducer may enter the body from an access location outside the body, such as through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means.
Stents, grafts, stent-grafts, vena cava filters, expandable frameworks, and similar implantable medical devices are radially expandable endoprostheses which are typically intravascular implants capable of being implanted transluminally and enlarged radially after being introduced percutaneously. Stents may be implanted in a variety of body lumens or vessels such as within the vascular system, urinary tracts, bile ducts, fallopian tubes, coronary vessels, secondary vessels, etc. They may be self-expanding, expanded by an internal radial force, such as when mounted on a balloon, or a combination of self-expanding and balloon expandable (hybrid expandable).
Depending on the structure and conditions of a body lumen, stents can be prone to stent migration.
One way to reduce the risk of stent migration has been to expose bare metal portions of the stent to lumen tissue. The open, braided structure of the stent may provide a scaffold that promotes tissue ingrowth into the stent. This tissue ingrowth may aid anchoring the stent in place and may reduce the risk of migration. In some cases, however, tissue ingrowth has been known to lead to reocclusion of the body lumen. In addition, stents anchored by tissue ingrowth cannot be moved or removed without an invasive procedure. To reduce tissue ingrowth, stents have been covered with a coating (e.g., made of a polymer, etc.) to create a physical barrier between the lumen and the lumen wall. However, in some circumstance, such stents can have an unacceptable occurrence of migration, as compared to bare metal counterparts.
Another way to reduce the risk of stent migration has been to use a flared stent. However, stents having flares can have an unacceptable occurrence of migration.
All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
Without limiting the scope of the present disclosure a brief summary of some of the claimed embodiments is set forth below. Additional details of the summarized embodiments of the present disclosure and/or additional embodiments of the present disclosure may be found in the Detailed Description below.